Hit Redline

iTrader: (2)

Hey Guys,

Just looking for a little insight and thoughts on my issue.

Seems compression on ,my front rotor is fine. My back rotor has compression on only one rotor side, the other two sides show 0 compression. The only reason I thought something might be wrong was I began to hear a ticking sound. Sounded like an exhaust leak. The car idles fine and runs good.

Has anybody seen this before?

I tried unsticking the seals with ATF assuming that might be the issue. Soaked the ATF for a few days and cranked a couple of times a day. Results were the same.

I am using a mazda rotary compression tester.

Here is a pic of the car burning off the ATF.

Also not sure if it matters but, the is a J-spec motor TII motor.

Hit Redline

iTrader: (2)

forgot the pic

Kim

So did you own the car when it had full compression?
I'm sure that if you manage to get the seals unstuck, assuming that's the problem, you will feel a big difference in power.
My old motor ran great with 70-80psi compression, but it consumed water like an elephant.

And I just got myself a new desktop picture LOL

Hit Redline

iTrader: (2)

Yes it did have full compression. I had the TII swap done and it was fine for 200 miles. There seems to be very little power loss since the ticking started.

My plans are to just to a rebuild and streetport at this point. I don't want to damage the housings if the seals are cracked.

Rx-7Doctor

iTrader: (13)

Was this a high mileage motor that you took out of another car?

680RWHP12A

yah, this is a strange one guys.. the car runs fine, besides a slight popping from the intake, and a little down on powerto me it sounded like a stuck or broken seal, so we mmo'd it for a few days, started it, and the sound is still there..
i did compression tests with the rotary engine compression tester (about 10 times, lol)
befor and after the mmo, no changes.. acording to the compression tester 2 sides of the rear rotor have 0 compression! i dont see how thats possible considering the car still runs good

either way, i will be taking care of you chris......

Hit Redline

iTrader: (2)

Exact mileage is unknown. Somthing like 50 to 60 thousand.

680RWHP12A

nope, low mileage j-spec motor

it had some stuck seals(very minor but im picky) on intital startup , but after running the motor for about 2 hours it sounded good and ran like a bat outa hell!
good compression #'s too

Hit Redline

iTrader: (2)

No worries here robert, just that I would share this.

680RWHP12A

kilometers chris, lol

bridgeit

i have a couple motors for sell cheap!!!

680RWHP12A

LOL
thanks, that helps us alot buddy

680RWHP12A

im glad you did..
if you could upload a small clip of the car idiling and revving upthat would be wonderful... its unbelievable how good it sounds.. i still dont see how 2 sides of the rear rotor are 0 ..
anybody have ideas?

Rx-7Doctor

iTrader: (13)

Pretty strange to see that type of compression reading. What did the rear plugs look like?

680RWHP12A

front and rear spark plugs are black,(no color difference between the front and read either)its on the rich side.. i tuned it with a wideband in the 11:50 afr range

Nate83SA22

thats wierd lol....I'm only 16 and still learning about rotary engines and that sounds kinda wierd? runs with Bad Compression maybe. Runs good with no compression Hmmmmm....

RX3SP

iTrader: (62)

I'm going to guess the the springs under one of the apex seals have very little to no tension and that apex seal does not make contact with the housing under cranking speed but once the engine is running centrifugal force causes the apex seal to make enough contact with the rotor housing to seal relatively well.

jjenibun

I just purchased a 1985 12a rotary, for $250.00. The guy that I purchased it from at the salvage said that the engine had no compression. When I get the engine home, I will test it to see if it is carbon locked. But if he tried to start it and this is what he found, chances are that it is not locked. My question is if it is the compression, would the engine have to be rebuilt, or is there something that I can do to get the compression back. This is my first go at a rotary engine. Thanks inadvance Johnny

OneRotor

iTrader: (3)

actually, it's the exact opposite, seals chatter at high RPM because of centripital force. The "centrigugal force" that you're talking about is known as an imaginary force. If you take any higher level physics course, you will find this out. Blood centrifuges rely on this principal. I have no clue what would cause a motor to do this, but rotaries are known for running under strange circumstances. My 12a's timing is 90* retarted, and while she's a ***** to start, she runs like a bat outta hell up until ~6k in 4th gear, when I get detonation.

trochoid

iTrader: (6)

Welcome to the forum and the Darkside Johnny. generally we don't step on someone else's thread, but since your new and this is your 1st post, your forgiven, lol.

I would try the atf treatment to try and loosen the seals. Look in the exhaust ports and check for carbon buildup, push the apex seals to see if they still have any spring to them. Also check for rust and any traces of coolant in the housings. If there is anything more than light surface rust or the housings are full of coolant, the engine is probably toast.

For your reading pleasure as a new member, in my sig line is a link to the online FSMs, carb manual and other related books.

OneRotor

iTrader: (3)

start your own thread and your answer will be answered quickly. but here is some advice. Take a ratchet with (i think) a 13/16" socket on it, put it on the bolt on the front pulley, and gently try to rotate the motor. If the front pulley is stuck, don't force it. pull the plugs, pour MMO, ATF, diesel, or SeaFoam down through the carb, put some in the plug holes, and let it sit for a few days. try and turn it over after that with the front pulley. If it starts to move, turn it over 2-3 times, put the plugs back in, and then put the same stuff that you used before down the carb, turn it 1/3 of a turn, put more down the carb, turn 1/3, put more down the carb, and turn it over a few times. leave for a few days, and keep on doing it until it turns over easily. when you pur the stuff down the carb, put 2-3 ounces down per rotor side.

RX3SP

iTrader: (62)

Whitey, I fully understand the idea of centrifugal force being an imaginary force by many physics experts and I'll have to agree for Newton's laws to be valid, centrifugal force needs to be an imaginary force.
I didn't write my guess on why maybe his engine ran well with no compression on two sides of one rotor at cranking speed to debate whether centrifugal force is real or imaginary. That debate has raged among plenty of people who know more about physics than either of us for a long time and likely the debate won't be solved here or anywhere else anytime soon!
I'll concede the technical point in this instance that centrifugal force is imaginary....BUT it appears to be quite real to the object being rotated. This is because the object being rotated "thinks" that it is in a non-accelerating situation, when in fact it is not. Take for an example a child being spun on a merry-go-round. The child, based on strict Newtonian physics is not experiencing any real outward force, yet he still must exert a force to prevent himself from being thrown off the merry-go-round. The greater the mass of the child and the greater the speed of rotation the harder it is for the child to prevent himself from flying off the merry-go-round. Because centrifugal force "seems" so real, I think in this case it helps to pretend that it is!

Rx-7Doctor

iTrader: (13)

And detonation is a good thing? Recommend you correct your timing before you start spitting pieces of your apex seals out.
Small correction on socket size. It's a 19mm head on the E-shaft bolt.

trochoid

iTrader: (6)

Centripetal, cetrifugal, who cares. The housing is holding the seal in semi-circular path but the seal wants to continue it's motion tangentially to the curve, that's why it moves outward and seals.

aussiesmg

iTrader: (1)

wierd, watching this one to see what it turns out to be......take pics guys.....